考虑空间变异性的隧道砂层注浆加固体稳定性分析

Stability Analysis of Tunnel's Sand-Layer Grouting-Reinforced Body Considering Spatial Variability

为研究水泥浆液析水效应导致的砂层注浆加固体空间变异性问题,开展注浆加固体空间变异性试验研究,提出砂层注浆加固体性能衰减率的概念及衰减率的空间分布简化公式。在此基础上,进行隧道穿越砂层注浆加固体有限元数值模拟,以隧道拱顶沉降与隧道涌水量作为评价隧道稳定性的指标,研究考虑砂层注浆加固体空间变异性的必要性和加固圈厚度、水泥浆液水灰比(W/C)对隧道稳定性的影响。研究结果表明:1)水灰比对渗透注浆加固效果的空间分布有明显影响,W/C≥1.2时,砂层渗透注浆加固体性能存在显著的空间非均匀性,注浆加固体底部区域的抗压强度及变形模量明显高于上部区域,注浆加固体性能与位置高度呈负相关关系;W/C≤1.0时,析水效应对注浆加固体性能的影响可忽略。2)当W/C≥1.2时,数值计算模型中考虑砂层注浆加固体空间变异性所得的拱顶沉降量、隧道涌水量明显大于不考虑时所得的拱顶沉降量、隧道涌水量,因此考虑砂层注浆加固体空间变异性非常必要。3)隧道拱顶沉降量、延米涌水量随注浆加固圈厚度的变化呈非线性特征,加固圈厚度过大时,上述2个指标随注浆加固圈厚度增加而减小的速率明显降低,不利于隧道注浆经济性。4)浆液水灰比的增加不利于隧道拱顶沉降量与隧道涌水量的控制,工程在可渗透的前提下,砂层注浆应该尽量选用低水灰比的水泥浆液。

To investigate the spatial variability of a sand-layer grouting-reinforced body based on the water bleeding effect of cement slurry,experiments are conducted and the concept of attenuation rate of sand-grouting performance as well as the simplified equation of spatial distribution of attenuation rate is proposed.Accordingly,stability analysis is performed on a tunnel's grouting-reinforced body under-crossing sand layer by using a finite element simulation method.The crown settlement and water inflow of the tunnel are used as indices to evaluate the tunnel stability and validate the necessity of considering the spatial variability as well as the influence of the thickness of the reinforcement ring and the water-cement ratio of the cement slurry on the tunnel stability.The results show that:(1)The water-cement ratio has a significant influence on the spatial distribution of the grouting-reinforced body performance.When the water-cement ratio is≥1.2,the performance of the grouting-reinforced body is nonlinearly distributed spatially.In addition,the compressive strength and deformation modulus at the bottom are significantly higher than those at the top.Furthermore,the performance of the grouting-reinforced body is negatively correlated with the height of the position.However,when the water-cement ratio is≤1.0,the impact of the water bleeding effect on the grouting-reinforced body performance can be ignored.(2)When the water-cement ratio is≥1.2,the crown settlement and water inflow of the tunnel obtained by considering the spatial variability are both significantly larger than when ignoring the spatial variability and considering the spatial variability of the grouting-reinforced body is of vital importance.(3)Finally,the crown settlement and water inflow of the tunnel present nonlinear characteristics with the change of the thickness of the grouting-reinforced body ring.These two indices decrease with the increasing thickness,and the decreasing rate significantly declines when the thickness of the grouting-reinforced body ring is extremely large;this is unfavorable to economic consideration.(4)The increase in the water-cement ratio is unfavorable to the control of the crown settlement and water inflow of the tunnel.In addition,a lower water-cement ratio should be chosen in the sand grouting engineering under the premise of infiltration.